1. Field of the Invention
This invention relates to a combustion engine of which the pistons are provided with a combustion chamber and which comprise means for protecting the edge of the opening of the combustion chamber from the formation of cracks.
2. Description of the Prior Art
German Pat. No.: 745,396 describes a method of protecting the edge of the mouth, in the case of pistons subjected to a considerable loading, by constructing the said edge of a material of higher thermal resistance than that of the piston itself. Although the edge of the mouth can be thus effectively protected against the formation of cracks due to the high and continually changing incidence of the temperature, this method nevertheless increases the weight of the piston. Constructions are therefore known in which heavy metal inserts of the aforementioned type are dispensed with. In German Specification No: 1,122,325 for example, the edge of the opening is protected by a pure aluminium layer applied by the building-up welding process, while German Specification No: 2,124,595 describes a method of refining a light-metal piston, in the zone of the said edge, by re-melting it with a charge-carrier ray, thus rendering it resistant to cracks. This otherwise very useful solution, however, suffers from the drawback of the considerable production cost involved.